a) Field of the Invention
This invention relates to a pulley block and in particular a pulley block having a body rotatably supporting a sheave and a mounting pin by means of which the block may be connected to some other component.
Though the pulley block of this invention may be used in a variety of circumstances, it has a particular application in relation to racing dinghies. As such, it will be described exclusively with reference to that use, even though the invention is not to be regarded as limited to that use.
b) Description of the Prior Art
Pulley blocks are used extensively on the running rigging of racing dinghies, to assist in the hoisting and trimming of the sails. Such pulley blocks are required to have very low friction in order to minimise losses and also to have relatively low weights. Further, such blocks must have some kind of mounting arrangement, whereby the block may be connected to some other component of the dinghy.
A common mounting arrangement for a pulley block of the kind described above is to furnish the body of the block with a pin which projects from the block body, at right-angles to the axis of rotation of the pulley. Depending upon the intended use of the block, the pin may be provided with a variety of different connection arrangements but typically the pin will have a transverse hole externally of the block body and to which a shackle may be secured. In some blocks, the mounting pin is securely held against rotation with respect to the block body, whereas with others, the pin is freely rotatable with respect of the block body.
It has been recognised that there are advantages in providing a block with a mounting pin which may be allowed freely to rotate, but which may also be locked against rotation, as required by the sailor. Various mechanisms have been proposed for this and it is also known to provide a mechanism which allows a pin either freely to rotate with respect to the body or which is permitted only a limited range of movement. These mechanisms add to the overall weight of the block and may also reduce the reliability, when the block is being used under extreme conditions.